Knowing how to calculate the circumference of a circle can be useful in everyday life, such as to help with craftsman work, or to position a fence around a hot tub, or to solve math problems at school, or something else. If you want to know how to calculate the circumference of a circle, follow these steps.
Step
Method 1 of 2: Using Diameter
Step 1. Write down the formula to find the circumference of a circle using diameter
The formula is simple: C = d. Here "c" represents the circumference of the circle, and "d" represents its diameter. This means that you can find the circumference of a circle simply by multiplying the diameter by pi. Enter into the calculator to give it a value of 3, 14 or 22/7.
Step 2. Plug the diameter value into the formula and calculate
- Example problem: there is a hot tub with a diameter of 8 meters, and you want to build a fence that creates a 6 meter wide space around the tub. To find the circumference of the fence to be made, you must first find the diameter of the tub and railing, which would be 8 meters + 6 meters + 6 meters, which would account for the entire diameter of the tub and fence. The value of the diameter is 8 + 6 + 6, or 20 meters. Now plug it into the formula, enter into the calculator, then calculate:
- C = d
- C = x 20
- C = 62.8 meters
Method 2 of 2: Using Fingers
Step 1. Write down the formula to find the circumference of a circle using the radius
The radius is half the length of the diameter, so the diameter can be considered as 2r. Remember, the formula for finding the circumference of a circle with radius: C = 2πr. In this formula, "r" is the radius of the circle. Again, enter into the calculator to get a numerical value closer to 3, 14 or 22/7.
Step 2. Plug the radius into the formula and calculate it
For this example, let's say you're cutting a decorative strip of paper to wrap around the edges of a cake. The radius of the cake is 5 cm. To find the circumference, simply plug the radius into the formula:
- C = 2πr
- C = 2π x 5
- C = 10π
- C = 31.4 cm.
Tips
- You should buy a sophisticated calculator that already has the button. This will save time and the answer will also be more accurate, because the key yields a much more accurate approximation to than 3, 14.
- Remember: some questions may ask you to replace pi with 3, 14 or 22/7.
- To find the circumference of a circle from its diameter, simply multiply pi by the diameter of the circle.
- The radius of a circle is always half the length of its diameter.
Warning
- Practice often.
- If you get stuck, ask a friend, family member or teacher for help. They will always help!
- Remember to always double-check the results of your calculations, because one mistake can destroy all your data.
